In a mobile communication system, an RF (Radio Frequency) block is designed to support several frequency bands, and in particular, capacitors used in a filter directly related to frequency bands must utilize a variable capacitor (also called variable reactance) having a different capacitance value at each frequency band.
In addition, a voltage controlled oscillator (VCO) among components of an RF block can obtain a change in capacitance value by adjusting a voltage applied to a variable capacitor, and thus alter a resonant frequency.
As such, a variable capacitor is a very important device in a tunable filter or a voltage controlled oscillator of an RF block.